1. Field of the Invention
The present invention relates to a system for fixing a sensor in a housing.
2. Description of the Related Art
Published German patent application document DE 197 31 420 A1 describes a device for detecting the pressure and the temperature in the intake manifold of an internal combustion engine and a method for manufacturing it. A temperature sensor and a pressure sensor fastened together with an evaluation circuit to a substrate with as little stress as possible are situated in a shared housing. The housing includes at least two spaces separated from one another, one of which forms a pressure space which is sealed off from the environment and is connected to the intake manifold via a connector, the part of the substrate on which the pressure sensor is attached being situated in the first space, and the second of which is used for accommodating and fastening the remaining part of the substrate having connecting elements, adhesive seals that decouple mechanical stresses being provided for sealing the pressure sensor and fastening the substrate.
NTCs (negative temperature coefficient thermistors) are frequently used for temperature measurements in pressure and air mass sensors in use today. NTCs are temperature-dependent resistors whose electrical resistance varies with temperature. NTCs normally include a smooth glass or plastic bead of approximately 1 mm to 3 mm in size and two connecting pins representing the electrical terminals.
Current response times t63, which apply to a temperature jump from 20° C. to 80° C., at an incident flow rate of v=6 m/s and installation in the pressure connector of a commonly used pressure sensor, are between 6 seconds and 10 seconds. However, significantly shorter response times than response times t63 of between 6 seconds and 10 seconds are frequently required.
Moreover, the NTC must have very good mechanical protection and support, since it is highly susceptible to flow-induced vibrations, and thus the mechanical loads of the connecting leads, i.e., the aforementioned two pins, become too great over the service life. In addition, the NTC must be protected against mechanical damage when the sensor is installed. To prevent the connecting leads from breaking, the NTC is protected all around in pressure and air mass sensors manufactured presently. This mechanical protection makes the heat transfer from the NTC to the ambient air very poor. On the one hand, the NTC is thermally very well connected to the thermally inert sensor housing; on the other hand, the flow through the cage that surrounds the NTC is almost completely shielded.